Ultrathin Parylene-C Membranes for Cell Growth
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Solution Overview
Problem
Existing biomedical membranes, particularly those made of parylene C, are not permeable to nutrients and waste, limiting their application in cell culture and medical devices, and existing porous membranes have fabrication challenges and surface topologies that disrupt cell growth.
Innovation Solution
Manufacturing a semipermeable parylene C membrane with ultrathin thicknesses (0.01 μm to 5 μm) and spatially interspersed thin and thick regions, allowing for permeability to proteins while preventing cell growth on one side and providing mechanical support on the other, using lithographic techniques and chemical vapor deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If parylene C is used as a conformal coating, then water tightness and pinhole-free properties are achieved, but permeability to nutrients and waste is lost
Solution Approach 1:
The patent applies porous materials by creating a track-etched porous membrane structure within the parylene C coating. Heavy-ion bombardment creates micropores through the film, and subsequent chemical etching enlarges these pores to enable nutrient permeability while maintaining the overall structural integrity and water-tight sealing function of the parylene C material.
Solution Approach 2:
The patent applies local quality by creating spatially varying pore distributions and thickness variations within the membrane. The track-etching process creates localized porous regions with controlled pore sizes and densities, allowing different areas of the membrane to have optimized properties for specific functions such as nutrient transport versus structural support.
2Object-generated harmful factors
If porous membranes are used for nutrient permeability, then cell growth is supported, but surface topology disrupts cell growth and mechanical strength is reduced
Solution Approach 1:
The patent applies parameter changes by precisely controlling the membrane thickness (ranging from ultrathin 0.01 μm to 5 μm) and pore size parameters. By optimizing these physical parameters, the membrane achieves adequate mechanical strength for its application while maintaining sufficient permeability for nutrient transport. The thickness and pore size are tuned to balance structural integrity with transport functionality.
Solution Approach 2:
The patent applies local quality by creating regions with different thicknesses and pore densities within the same membrane structure. This allows localized optimization where certain areas provide enhanced mechanical support while other areas maximize permeability for nutrient transport, resolving the contradiction between strength and permeability.
3Object-generated harmful factors
If track-etching is used to create pores, then permeability is achieved, but fabrication complexity increases
Solution Approach 1:
The patent applies preliminary action by first depositing the complete parylene C coating to the desired final thickness before performing any pore creation steps. This preliminary coating formation establishes the base membrane structure with controlled thickness, and subsequent track-etching and chemical etching steps then create pores without requiring multiple coating-deposition cycles, thereby simplifying the overall fabrication process.
Solution Approach 2:
The patent applies merging by combining multiple functions into a single integrated membrane structure. The track-etched porous membrane simultaneously provides structural support, nutrient permeability, and cell growth support without requiring separate layers or components, thereby reducing overall device complexity despite the sophisticated etching process used to create the porous structure.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The semipermeable membrane facilitates optimal cell growth with a smooth surface for nutrient diffusion and mechanical strength, suitable for various biomedical applications, including in vivo tissue replacement and cell culture, while preventing cell adherence on the rough side.
Implementation Method 1
the membranes must be permeable to nutrients (and waste from cells), such as proteins in serum
Implementation Method 2
Parylene C—which has been found to be permeable to proteins in serum at ultrathin thicknesses (e.g., 0.01 μm to 5 μm thick)—is manufactured into a membrane
Data Source
AI summary
Thin parylene C membranes having smooth front sides and ultrathin regions (e.g., 0.01 μm to 5 μm thick) interspersed with thicker regions are disclosed. The back sides of the membranes can be rough compared with the smooth front sides. The membranes can be used in vitro to grow monolayers of cells in a laboratory or in vivo as surgically implantable growth layers, such as to replace the Bruch's membrane in the eye. The thin regions of parylene are semipermeable to allow for proteins in serum to pass through, and the thick regions give mechanical support for handling by a surgeon. The smooth front side allows for monolayer cell growth, and the rough back side helps prevents cells from attaching there.